Carbonyl compounds including ketones such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and acetone, and aldehydes typified by acetaldehyde are useful as solvents and chemical raw materials, and hence used in various fields. Such carbonyl compounds are generally manufactured by two-step reaction methods in which an alcohol produced by hydrating an olefin is dehydrogenated. Meanwhile, as simpler methods, one-step reaction methods have also been known in which an olefin is directly oxidized.
The Wacker process using a PdCl2/CuCl2 catalyst has been known as one of the methods for directly oxidizing an olefin. This process is effective for the oxidation of terminal olefins each having a carbon-carbon double bond (hereinafter abbreviated as a “C═C bond”) at a terminal of a molecule thereof. However, this process has a problem of a low reactivity when used for oxidation of internal olefins each having a C═C bond at a position other than its terminals. This process also has a problem that if the number of carbon atoms of the olefin is increased, the reaction rate is markedly lowered. For this reason, in the industrial field, the use of the Wacker process is limited to only manufacturing of lower carbonyl compounds such as acetaldehyde and acetone, which are obtained by oxidizing lower terminal olefins.
To solve such problems involved in manufacturing a carbonyl compound by direct oxidation of an olefin, various methods have been proposed. For example, Tetrahedron Letters, 1985, 2263-2264 (NPL 1) discloses a method in which terminal and internal olefins are oxidized by using a palladium catalyst, a copper catalyst, polyethylene glycol, and water.
Japanese Unexamined Patent Application Publication No. Hei 5-140020 (PTL 1) discloses a method for manufacturing a carbonyl compound, in which method an olefin is oxidized in an acidic aqueous solution with molecular oxygen in the presence of palladium, an oxoacid salt of a metal having a redox activity (such as copper or iron), a hydroquinone, and a compound capable of converting the hydroquinone into a quinone (such as iron phthalocyanine, or cobalt tetraphenylporphyrin).
Japanese Unexamined Patent Application Publication No. Hei 5-148177 (PTL 2) discloses a method for manufacturing a carbonyl compound, in which method an olefin is oxidized in a solution containing water and urea in the presence of a catalyst comprising a palladium compound and a copper compound and/or an iron compound.
Japanese Unexamined Patent Application Publication No. Hei 7-17891 (PTL 3) discloses a method for manufacturing a carbonyl compound, in which method an olefin and water are allowed to react with each other in the presence of a palladium compound, a copper compound, and an organic phosphorus compound.
Japanese Unexamined Patent Application Publication No. Hei 7-149685 (PTL 4) discloses a method for manufacturing a carbonyl compound, in which method an olefin and oxygen gas are allowed to react with each other in a solvent of an oxygen-containing compound or a sulfur-containing compound in the presence of a palladium compound, a polyoxoanionic compound, and an iron-containing compound.
J. Org. Chem., 1990, 55, 2924-2927 (NPL 2) discloses a modified Wacker process in which a cyclic or internal olefin and p-benzoquinone are allowed to react with each other in the presence of a palladium catalyst by use of a strong acid. Meanwhile, Japanese Unexamined Patent Application Publication No. Hei 8-67648 (PTL 5) discloses a method for manufacturing a ketone, in which method an olefinic compound is oxidized in the presence of water and a palladium compound by use of p-benzoquinone, and the oxidation reaction is conducted by using a heterogeneous strong acid (for example, an sulfonic acid ion exchanger or the like).
J. Chem. Soc., Perkin Trans. 1, 2000, 1915-1918 (NPL 3) discloses an oxidation reaction of an olefin, using pyridine and 2-propanol, in toluene in the presence of palladium acetate.
Japanese Unexamined Patent Application Publication No. 2002-191979 (PTL 6) discloses a method for manufacturing a ketone, in which method an alkene is oxidized with molecular oxygen in the presence of an oxidation catalyst comprising a palladium compound, a heteropolyacid, and a strong acid.
Japanese Unexamined Patent Application Publication No. 2008-231043 (PTL 7) discloses a method for manufacturing a ketone, in which method an olefin is allowed to react with molecular oxygen in the presence of a palladium source, a mesoporous silicate, water, and a protonic acid.
However, the conventional methods for manufacturing a carbonyl compound are not yet sufficiently satisfactory methods for manufacturing a ketone at a high yield and a high selectivity by oxidizing an internal olefin or a cyclic olefin.
Meanwhile, Angew. Chem. Int. Ed., 2006, 45, 481-485 (NPL 4) discloses a method for manufacturing a ketone, in which method molecular oxygen is used as a reoxidizing agent when a terminal olefin is oxidized in a polar solvent such as N,N-dimethylacetamide in the presence of a palladium catalyst.